Rep. Pete King, R-N.Y., chairman of the committee has vowed this will be the first in a series of sessions.

The hearing at times has been emotional. Rep. Keith Ellison, D-Minn., one of two Muslims in Congress, broke down as he recounted the story of a young Muslim-American man killed in the 9/11 attacks.

Marvin Bledsoe spoke about how his son, Carlos, converted to Islam and got training in Yemen before eventually killing an Army private. Abdirizak Bihi described how his nephew was lured to Somalia to join Al Shabab, an Islamic extremist group, and was killed.

Update at 11:13 a.m. ET

The House Homeland Security Committee is questioning witnesses about the radicalization of Muslims in America.

Rep. Bennie Thompson, D-Miss., is asking whether Muslims living in the USA should be profiled. He is opposed to the idea.

"You run the risk of profiling law-abiding citizens in the country who happen to be Muslims," he said.

Update at 10:48 a.m. ET

"Americans are sitting around doing nothing about radical extremists," says Marvin Bledsoe, whose only son turned to terrorism after being radicalized in Yemen.

Bledsoe is testifying before the House Homeland Security Committee, which is holding a controversial hearing on the radicalization of Muslims.

"We are losing American babies," Bledsoe said. "This country has to stand up and do something. ...Tomorrow, it could be your son or your daughter."

Update at 10:42 a.m. ET

Marvin Bledsoe talks about how his son, Carlos, grew up with Martin Luther King Jr.'s picture on his wall. He is explaining how Carlos was "brainwashed" after converting to Islam and was radicalized at a training facility in Yemen.

Carlos Bledsoe, now known as Abdulhakim Mujahid Muhammad, admitted in 2008 that he shot Army Pvt. William Long. The elder Bledsoe opened his remarks by expressing sympathy to Long's family.

Update at 10:28 a.m. ET

Rep. Frank Wolf, R-Va., has finished his testimony and we're moving to a panel of witnesses. Among them are relatives of two Americans who were inspired by radical Muslims to turn to terrorism.

The Associated Press reports that Marvin Bledsoe will discuss his son, Carlos, who is charged with killing an Army private. Carlos Bledsoe has converted to Islam.

"Carlos was captured by people best described as hunters," Bledsoe says, according to prepared remarks. "He was manipulated and lied to."

Update at 10:19 a.m. ET

Ellison is getting visibly upset, choking back tears as he recounts the story of a Mohammad Hamdani, a 23-year-old Muslim-American paramedic who died in the Sept. 11, 2001 attacks.

Hamdani was called the "All-American Jedi" by The New York Times, because he was a fan of the Star Wars movies. Hamdani was one of the first responders on the scene during the worst terrorist attacks on U.S. soil, and was among more than 20 Muslim-Americans who died on 9/11.

"He gave his life to help other Americans," Ellison said.

The congressman, sobbing openly by the end of his remarks, reminds the committee that Muslims in the USA are "just like the rest of us" -- police officers, paramedics and even members of Congress.

Update at 10:07 a.m. ET

Ellison, first elected in 2006, said politicians and law enforcement need to do more to build trust with the Muslim community and to lessen "suspicion" of the millions of Muslims living in the United States.

"The best defense is social engagement," he said.

Update at 10:01 a.m. ET

Rep. Keith Ellison, D-Minn., one of two Muslims in Congress, is speaking. He said he doesn't agree with the committee's approach to investigating violent extremism. He worries that the hearings and targeting one community "could potentially threaten our security."

"Demanding a community response asserts that an entire community is responsible for the acts of a few," Ellison said. Assigning "violent attacks to one community are wrong."

He is concerned that there are too many stereotypes being perpetuated about Muslims, leading to fears about the community as a whole.

Update at 9:49 a.m. ET

King has finished. Rep. Bennie Thompson of Mississippi, the top Democrat on the Homeland Security Committee, is now speaking and publicly raising his objections to what he considers a "narrow" hearing focused only on one group.

"I urge the chairman to hold a hearing examining the homeland security threat posed by anti-government and white supremacist groups," Thompson said. "...A narrow focus that excludes known threats lacks clarity and may be myopic."

Update at 9:39 a.m. ET

Security is tight today in Congress as controversial hearings about the terror threat posed by radicalized Muslims begin.

Rep. Pete King, R-N.Y., asked for the U.S. Capitol Police to be on hand as the House Homeland Security Committee explores the threat posed by some Muslims in the United States who are being radicalized by terrorist groups.

In his opening remarks, King acknowledged the controversy generated by the hearing but stood firm about its need. "To back down would be a craven surrender to political correctness and an abdication of what I believe to be the main responsibility of this committee -- to protect America from a terrorist attack," he said.

King added: "This committee cannot live in denial."

He argued that the hearing "is the logical response to the repeated and urgent warnings which the Obama administration has been making in recent months."

The New York lawmaker brushed off protests by civil liberties and religious groups, pleas from his colleagues in Congress and threats made against him to convene the unusual session. King told the AP that he has had extra security from New York police for months because of the hearings, citing an overseas threat made in December.

A new USA TODAY/Gallup Poll finds a majority of Americans believe the hearings are appropriate, but do not believe Muslims in the United States are extreme in their beliefs. There are an estimated 2.6 million Muslims living in the USA.

Rep. Keith Ellison, D-Minn., one of two Muslim members of Congress, will testify. Other witnesses include family members of young men who allege they were brainwashed by radicalized Muslims to engage in deadly acts of terrorism.

Two sets of congressional Democrats urged King on Wednesday to cancel the hearing.

"It sends the wrong message to the Muslim-American community," House Minority Whip Steny Hoyer, D-Md., said in a statement. "We need them to work with law enforcement to identify terrorist threats, not be afraid of them. ...Targeting one segment of our population is not helpful to that objective."

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About Catalina Camia

Catalina Camia leads the OnPolitics online community and has been at USA TODAY since 2005. She has been a reporter or editor covering politics and Congress for two decades, including stints at The Dallas Morning News and Congressional Quarterly. Follow her at @USATOnPolitics.